Definition of underhanded:
sneak, secret, indirect, confidential, clandestine, honest, classified, hole-and-corner, behind-the-scenes, hush-hush, shadowy, shifty, underhand, deceptive, surreptitious, corrupt, privy, rogue, duplicitous, private, disingenuous, hugger-mugger, stealth, undercover, crooked, sharp, underground, shady, fast, bent, underarm, guileful, sneaky, sneaking, backstairs, covert, mysterious, double-dealing, furtive, stealthy, lubricious, in strict confidence.
- dishonest (part of speech: adjective)
- secret (part of speech: adjective)
- "Captivating Mary Carstairs", Henry Sydnor Harrison.
- "The Children of the World", Paul Heyse.